Mechanical fasteners are widely used for joining together two or more metal members. In most applications of mechanical fasteners, holes are formed through the workpieces to be joined, the holes are aligned, and a fastener is passed through the holes and secured. Generally, the fastener has enlarged head portions at each end to prevent the workpieces from being separated, and may also be designed to apply clamping pressure between the head portions so that the workpieces are firmly held together.
This conventional process of joining via mechanical fasteners has a number of disadvantages. For instance, machining the holes for the fasteners results in increased manufacturing cost. Moreover, the head portions of the fasteners represent added weight and cost to the structure being manufactured. For a structure using many such fasteners, the additional weight and cost of the fastener heads can be significant. Additionally, in many cases a sealant must be applied in the holes through which the fasteners extend in order to provide protection against corrosion or to otherwise seal the joints. Furthermore, the holes in the workpieces cause stress concentrations and thereby weaken the structure, so that thicker members and/or higher strength materials must be used in order to meet design safety margins. Thus, the conventional mechanical fastening process leads to increased weight of the final product, and increased cost for manufacturing the product.